Light sources comprising a light emitter inside an outer envelope are known per se and include, for example, ancient and well known incandescent light sources. These incandescent light sources are still used extensively as they are relatively easy to manufacture and because many optical systems of, for example, luminaires are designed and optimized to use the light distribution coming from these incandescent light sources. A well known drawback of the incandescent light sources is that they have a relatively low efficiency as they emit a large part of their energy in the infrared part of the electromagnetic spectrum. As such, many replacement light sources have been developed for replacing the incandescent light sources, for example, the compact fluorescent light sources, and, more recently, light sources comprising light emitting diode devices. These replacement light sources clearly have improved efficiency compared to incandescent light sources.
An example of a retrofit lamp comprising light emitting diode devices as light emitter may be found in the non-prepublished patent application “Illumination device with LED and a transmissive support comprising a luminescent material” of the current applicant, attorney docket PH009408, incorporated herein by reference. In the embodiment shown in FIG. 3 of the cited patent application the retrofit lamp is shown in which a light emitting diode is arranged inside a transmissive support which again is arranged inside a translucent exit window. A disadvantage of the above-mentioned retrofit lamp is that the emission profile in a plane perpendicular to the base of the LED is not wide enough.